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My simple, perhaps too simple, understanding of how breathable fabrics work is this:
You have a micro-pore membrane with holes in it of a certain critical size. Water in gaseous form can pass through the holes because the molecules are the size of a single water molecule each, which is pretty small. Water in liquid form, however, cannot pass through the membrane because *surface tension* prevents them from moving en masse through the holes.
So for a breathable shell to work, the liquid (water) inside has to be converted to gaseous form by heat. As the molecules heat up, they repel each other, also commonly referred to as pressure. Once the pressure inside the shell exceeds the pressure outside the shell, the water molecules tend to work their way through the membrane.
If you BS-o-meter is pegging at this point, check what I've said against this:
http://www.gore-tex.com/remote/Satellite/content/how-does-it-work
On the Gore-tex website.
So by this model, the best possible conditions for breathable fabrics to work are these:
1. The hotter and sweatier the wearer gets, the higher the internal pressure, the more the stuff breaths. This is best accomplished by being active in a very hot environment like, say, the dessert.
2. The lower the ambient (outside) humidity, the lower the pressure outside, the better the stuff will breathe.
Will it breath underwater? Well, alright, I'm willing to admit that if you had enough of an air space between the skin and the membrane for water to reach gaseous state, a small amount of gaseous water could probably be passed through the pores an into the mass of liquid water on the other side. *BUT*, there would have to be enough space for that to happen, and only gaseous water would pass out for the same reason that liquid water cannot pass in - the surface tension would prevent it from passing through the pores.
As for Gore-tex glove demonstration, what I think is more likely happening is one or both of these two things:
1.) Because the water covering the hand in the glove is ordinary tap water (presumably), it is being absorbed by the tissues of the skin via osmosis.
1 a.) This is accentuated by the fact the water is probably cold or at least cool (again, I presume) which prevents sweat from forming, dumping salt into the system and drawing more water out of the skin.
2.) The water in the tank which the glove is immersed in is salt water, at which point, once again osmosis kicks in - Gore-tex would act just like the membrane of the skin cells, and the liquid tap water which is relatively free of solutes would pass into the salty water the same way it passes into the skin cells.
Well... looks like I partially contradicted myself. I'll do some research and write up what I find somewhere, if people are interested.
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I simply do not believe it. New 
BoaterTalk 
